Wednesday was a big day in Washington, D.C., for anyone who likes fishing, rafting or canoeing public water in the United States.

In what is likely the most meaningful river-access case ever heard before the U.S. Supreme Court, PPL Montana vs. Montana is seeking to answer the long-disputed question of who really owns the riverbeds on navigable waterways, and whether the definition of “navigable” should be based on the present, or based on the river’s navigability when the state joined the union.

This case should greatly interest residents of Colorado, particularly considering the access debate that erupted on the Taylor River in 2010, a conflict that led to House Bill 1188 — the “Right to Float” bill, which led to Gov. Bill Ritter’s “River Access Dispute Resolution Task Force,” which led to the appointment in September of the three-person “River Access Mediation Commission.”

This case has implications far beyond Montana. Indeed, an executive from PPL, a Montana power company, might have put it best: “We welcome the Supreme Court’s decision to take up this case,” said Robert Grey, senior vice president of PPL, when the Supreme Court agreed back in June to hear the case. “Because of the broad implications it has for water users throughout the West.”

Twenty-six state attorneys general filed a joint amicus brief in support of the State of Montana, including Oregon, Washington, Idaho, Alaska, Nevada and New Mexico. But not Colorado. Why? For the answer, you need look no further than four of the organizations that filed amicus briefs in support of the power company — all from the Centennial State: the Colorado Cattlemen’s Association, Colorado Farm Bureau, Littleton-based Creekside Coalition, and — shocker alert — the Lakewood-based Mountain States Legal Foundation.

At issue is whether PPL, owners of several dams on Montana rivers, owns the land beneath the rivers that flow past its property. The case came to be in 2003 after two private citizens filed a lawsuit claiming that PPL owed the state back-rent for use of the lands.

This is where I have a problem with the other side in this case. The state ended up joining the private individuals in the suit, and a district court awarded Montana almost $50 million in damages. I’m nervous about the outcome of this case, and I hope that the power company loses big, but if attorneys for PPL are able to win — and anything is possible with our current Supreme Court — we might look back at this case that cost us a huge slice of our public domain and say that it was a greedy, opportunist overreach by Montana, not PPL, that set this ball in motion.

That this case comes out of Montana is not surprising. That it involves the Missouri, the Madison, and Clark Fork rivers is notable. As long as Montana access debates stayed focused on Big Sky backwaters like Mitchell Slough or the Ruby River, they hadn’t drawn much national attention. But these are three of the biggest, most popular, most fishable rivers in the West. If the beds and banks of these rivers can be given away to a private party, then it will be a fishing lodge land-grab and privatization stampede for many other waterways in the country.

Colorado already has the friendliest landowner laws in the nation in terms of riparian-zone property rights. But if the Supreme Court in this case rules for PPL, it will only embolden Colorado landowners to push for what many of them already feel they own: the river itself and the air above it. Nowhere was this more evident than on the Taylor, where one landowner compared rafting past his property to “walking across your lawn.”

And as for the 26 states that sided with Montana? All they would have to do if the court rules for PPL is change their river-access laws to match Colorado’s. Which is a wonderful thing — as long as you’re a riverfront landowner.

Tom Bie is a Colorado rafter, flyfisher and landowner. He is publisher of The Drake flyfishing magazine and lives in Fort Collins.